Face-to-face dies with a void for enhanced inductor performance

ABSTRACT

In accordance with the disclosure, an inductor may be formed over a semiconductor substrate of one or both dies in a face-to-face die arrangement while reducing the parasitic capacitance between the inductor and the adjacent die. In disclosed embodiments, a semiconductor device may include a void (e.g., an air gap) between the inductor and the adjacent die to reduce the parasitic capacitance between the inductor and the adjacent die. The void may be formed in the die that includes the inductor and/or the adjacent die. In some respects, the void may be etched in interface layers (e.g., comprising bump pads and dielectric material) between the semiconductor dies, and may extend along the length of the inductor.

BACKGROUND

It is sometimes not possible or practical to form a semiconductor devicefrom one integrated substrate (or semiconductor die) that includes allof the circuitry of the device. Thus, semiconductor devices have beenformed from two or more semiconductor dies. Forming a semiconductordevice from multiple dies may be challenging. For example, there may behundreds to thousands of connections required to transmit signalsbetween chips and to achieve high speed operation connection resistanceshould be low with short path lengths to minimize inductive andcapacitive effects. Further, as semiconductor devices scale and moretransistors are integrated into a device, the power and current levelsrequired to operate the transistors also may increase making powerdelivery more challenging. Additionally, semiconductor device yields maybe reduced, as the entire multi-die device may need to be discardedafter testing. Other challenges include arranging the components of thesemiconductor dies to avoid interference between the components that maydegrade device performance.

It may be desirable to form one or more inductors over the semiconductorsubstrate of one or both dies in a face-to-face arrangement, such as forhigh speed clock operation and/or power filtering, but interference froman adjacent die may degrade an inductor's performance. As such, thesetypes of inductors have not been used in semiconductor devices withface-to-face die arrangements.

SUMMARY

The present disclosure relates to approaches for enhancing semiconductorarrangements that include face-to-face semiconductor dies. In somerespects, one or both of the semiconductor dies may include an inductorformed over the semiconductor substrate of the die and a void betweenthe inductor and the other die to reduce parasitic capacitance.

Disclosed approaches provide for forming an inductor over thesemiconductor substrate of one or both dies in a face-to-face diearrangement while reducing the parasitic capacitance between theinductor and the adjacent die. In disclosed embodiments, a semiconductordevice may include a void (e.g., an air gap) between the inductor andthe adjacent die to reduce the parasitic capacitance between theinductor and the adjacent die. The void may be formed in the die thatincludes the inductor and/or the adjacent die. In some respects, thevoid may be etched in interface layers (e.g., comprising bump pads anddielectric material) between the semiconductor dies, and may extendalong the length of the inductor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present systems and methods for face-to-face dies with a void forenhanced inductor performance is described in detail below withreference to the attached drawing figures, wherein:

FIG. 1A is a diagram of an example of a cross-section of a face-to-facearrangement of semiconductor dies, in accordance with some embodimentsof the present disclosure;

FIG. 1B is a diagram of an example of a cross-section of a face-to-facearrangement of semiconductor dies, in accordance with some embodimentsof the present disclosure;

FIG. 1C is a diagram of an example cross-section of a face-to-facearrangement of semiconductor dies, in accordance with some embodimentsof the present disclosure;

FIG. 2 is a diagram of an example of a cross-section of a semiconductorpackage that includes a face-to-face arrangement of semiconductor dies,in accordance with some embodiments of the present disclosure;

FIG. 3A is a diagram of an example of a cross-section of a face-to-facearrangement of semiconductor dies that includes a void for an inductor,in accordance with some embodiments of the present disclosure;

FIG. 3B is a diagram of an example of a cross-section of a face-to-facearrangement of semiconductor dies that includes a void for an inductor,in accordance with some embodiments of the present disclosure;

FIG. 4A is a diagram of an example of a cross-section of a semiconductordie including probe pads for testing prior to including thesemiconductor die a face-to-face arrangement of semiconductor dies, inaccordance with some embodiments of the present disclosure;

FIG. 4B is a diagram of an example of a cross-section of a semiconductordie including additional interface layers formed over the probe pads ofFIG. 4A, in accordance with some embodiments of the present disclosure;

FIG. 4C is a diagram of an example of a top view of a testing tilestructure which may be included in a semiconductor die, in accordancewith some embodiments of the present disclosure;

FIG. 4D is a diagram of an example of a top view of an arrangement oftesting tile structures which may be included in a semiconductor die, inaccordance with some embodiments of the present disclosure; and

FIG. 5 is a flow diagram showing a method for testing at least onesemiconductor die prior to assembly in a face-to-face arrangement withanother semiconductor die, in accordance with some embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure relates to approaches for enhancing semiconductorarrangements that include face-to-face semiconductor dies.

The challenges in forming semiconductor devices from multiple dies hasimpacted the types of devices, configurations, and components found inmulti-die devices. Multi-die devices are often provided with diesmounted in a face-to-back arrangement. In particular, single dies areoften front to back so a stacked arrangement may naturally follow fromthis configuration by stacking similarly arranged dies. However, using aface-to-back arrangement may require all signals to be communicatedbetween the dies using Through Silicon Vias (TSVs) that extend throughthe entire bottom die. The size of the TSVs results in a lower densityof interconnects between the dies, thereby limiting performance anddesign flexibility. Further, the dies may be connected using microbumpsthat require an underfill that compromises the thermal performance ofthe composite structure.

A face-to-face arrangement may allow for significantly higher density ofinterconnects between the dies by forming interconnects from bump padmetal, but is a less natural arrangement and introduces significantchallenges from a design and fabrication standpoint. For example,semiconductor devices have not used a face-to-face arrangement ofsemiconductor dies that each include a graphics processing unit (GPU)due to these challenges. In such configurations, many signals may beneeded for the GPUs to communicate between chips, the GPU in asemiconductor die may require more power than can practically bedelivered, and die sizes may be large enough that yields areprohibitively low. Further, it may be desirable to form one or moreinductors over the semiconductor substrate of one or both dies, such asfor high speed clock operation and/or power filtering, but interferencefrom an adjacent die may degrade an inductor's performance. As such,these types of inductors have not been used in semiconductor deviceswith face-to-face die arrangements.

In contrast to conventional approaches, disclosed approaches provide forforming an inductor over the semiconductor substrate of one or both diesin a face-to-face die arrangement while reducing the parasiticcapacitance between the inductor and the adjacent die. In disclosedembodiments, a semiconductor device may include a void (e.g., an airgap) between the inductor and the adjacent die to reduce the parasiticcapacitance between the inductor and the adjacent die. The void may beformed in the die that includes the inductor and/or the adjacent die. Insome respects, the void may be etched in interface layers (e.g.,comprising bump pads and dielectric material) between the semiconductordies, and may extend along the length of the inductor.

Also in contrast to conventional approaches, disclosed approachesprovide for a TSV of a first semiconductor die that extends from asemiconductor substrate of the first semiconductor die on an insulatedpath through at least one metallization layer of the die to electricallyand mechanically connect to a different metallization layer to supplypower to the second semiconductor die. By extending the TSV, resistanceat higher layers (layers further from source) may be reduced allowingfor enhanced power delivery to the second semiconductor die. Resistancemay further be reduced by allowing for the TSV to electrically andmechanically connect to a thicker metallization layer than wouldotherwise be possible. In an example and non-limiting embodiment, thethicker metallization layer may have a highest thickness of all of themetallization layers (e.g., a topmost or near-topmost metallizationlayer of a metallization stack). Also, in some embodiments, themetallization layer that the TSV electrically and mechanically connectsto is capable of supplying power to both semiconductor dies. The firstsemiconductor die may be a top die or a bottom die in a face-to-facearrangement. Further, where additional dies are included in a die stack,any number of the dies may include one or more TSVs that extend from asemiconductor substrate of the die on an insulated path through at leastone metallization layer of the die to electrically and mechanicallyconnect to a different metallization layer to supply power to anotherdie.

In further contrast to conventional approaches, one or bothsemiconductor dies in a face-to-face arrangement may include a probe padlayer formed on a face of the die to allow the die to be individuallytested prior to assembly of the dies. Thus, faulty dies may be discardedindividually so they are not included in a composite semiconductordevice, thereby increasing device yields. The probe pad layer alsoallows dies to be matched so that a composite semiconductor deviceachieves desired performance, which may further increase device yields.

For example, where each die includes a number of processing cores,testing may be used to bypass faulty cores and select dies so that thecomposite semiconductor device collectively includes a threshold numberof active cores. In some embodiments, each semiconductor die may betested (e.g., at a fabrication facility pre-dicing), then additionalinterface layers (e.g., comprising bump pads and dielectric material)may be formed over the probe pad layer and used to bond thesemiconductor dies in a face-to-face arrangement to form a compositesemiconductor device. The composite semiconductor device may then betested using a different probe pad layer. In some embodiments, the probepads of the probe pad layer formed on the face of the die may be used toindividually test the die, and may remain inactive during operation ofthe composite semiconductor device.

With reference to FIG. 1A, FIG. 1A is a diagram of an examplecross-section of a face-to-face arrangement 102 of semiconductor dies,in accordance with some embodiments of the present disclosure. It shouldbe understood that this and other arrangements described herein are setforth only as examples. Other arrangements and elements may be used inaddition to or instead of those shown, and some elements may be omittedaltogether. Further, the drawings and illustrations in the presentapplication are not necessarily to scale, and do not necessarilyindicate actual relative dimensions.

The face-to-face arrangement 102 includes at least a semiconductor die104 and a semiconductor die 106. The semiconductor die 106 may include asemiconductor substrate 108, a metallization region 110, an interfaceregion 112, and an interface region 114. The semiconductor die 104 mayinclude an interface region 124.

As an overview, the semiconductor die 106 may include any number ofThrough Silicon Vias (TSVs), such as a TSV 120 and a TSV 122. While theface-to-face arrangement is described with respect to TSVs, such as theTSV 120 and the TSV 122, the TSVs may more generally be referred to asThrough Wafer Vias (TWVs) or Through Chip Vias (TCVs), as someembodiments may use a non-silicon material. One or more of the TSVs,such as the TSV 120 may extend from the semiconductor substrate 108 ofthe semiconductor die 106 through at least one metallization layer ofthe metallization region 110 to a metallization layer of themetallization region 110 to supply power to the semiconductor die 104through the metallization layer, the interface region 112 of thesemiconductor die 106, and the interface region 124 of the semiconductordie 104. By extending the TSV through at least one metallization layerof the metallization region 110, power distribution to the semiconductordie 104 may be enhanced.

The semiconductor substrate 108 includes semiconductor material, such assingle-crystal semiconductor material. In the present example, thesemiconductor substrate 108 is a silicon substrate and more particularlyis monocrystalline silicon. However, the semiconductor substrate 108 maycomprise any suitable semiconductor material(s), such as a group IVsemiconductor material or group III-V semiconductor material.

Group IV refers to a semiconductor that includes at least one group IVelement such as silicon (Si), germanium (Ge), and carbon (C), and mayalso include compound semiconductors such as silicon germanium (SiGe)and silicon carbide (SiC), for example. Group IV also refers tosemiconductor materials which include more than one layer of group IVelements, or doping of group IV elements to produce strained group IVmaterials, and may also include group IV based composite substrates suchas single-crystal or polycrystalline SiC on silicon, silicon oninsulator (SOI), separation by implantation of oxygen (SIMOX) processsubstrates, and silicon on sapphire (SOS), for example.

Group III-V refers to a compound semiconductor including at least onegroup III element and at least one group V element. By way of example, agroup III-V semiconductor may take the form of a III-Nitridesemiconductor. III-Nitride or III-N refers to a compound semiconductorthat includes nitrogen and at least one group III element such asaluminum (Al), gallium (Ga), indium (In), and boron (B), and includingbut not limited to any of its alloys, such as aluminum gallium nitride(AlxGa(1-x)N), indium gallium nitride (InyGa(1-y)N), aluminum indiumgallium nitride (AlxInyGa(1-x-y)N), gallium arsenide phosphide nitride(GaAsaPbN(1-a-b)), aluminum indium gallium arsenide phosphide nitride(AlxInyGa(1-x-y)AsaPbN(1-a-b)), for example. III-N also refers generallyto any polarity including but not limited to Ga-polar, N-polar,semi-polar, or non-polar crystal orientations. A III-N material may alsoinclude either the Wurtzitic, Zincblende, or mixed polytypes, and mayinclude single-crystal, monocrystalline, polycrystalline, or amorphousstructures.

One or more electronic circuits may be formed, at least partially withinthe semiconductor substrate 108. An electronic circuit may include oneor more transistors, such as a transistor 126. In the present example,the electronic circuit may form at least a portion of a GPU. Forexample, the semiconductor die 106 may be a GPU die. However, varioustypes and configurations of electronic circuits are contemplated asbeing within the score of the present disclosure. As some examples, thesemiconductor substrate 108 may include one or more circuit componentsof a processing unit, a Central Processing Unit (CPU), a singletransistor (e.g., a power transistor), a logic circuit, a power circuit,a System on Chip (SoC), and a transmitter and/or receiver. Where thesemiconductor substrate 108 includes a processing unit, the processingunit may include any number of cores. For example, where the processingunit is a GPU, the GPU may include multiple Streaming Multiprocessors(SMs) and each Streaming Multiprocessor may include a number cores.

The metallization region 110 may be formed on the semiconductorsubstrate 108 and comprise any number of metallization layers andinterlayer dielectric layers. Of the metallization layers shown in FIG.1A, a metallization layer 130, a metallization layer 132, and ametallization layer 134 are individually labeled. Also, of theinterlayer dielectric layers shown in FIG. 1A, an interlayer dielectriclayer 136 and an interlayer dielectric layer 138 are individuallylabeled. The metallization layers of the metallization region 110 mayinterconnect the various circuit components and/or electronic circuitsof the semiconductor die 106 and/or the semiconductor die 104. Thenumber of the metallization layers included in the metallization region110 and the thickness of those layers may vary depending on the designof the semiconductor die 106 and the circuit components and electroniccircuits included in the semiconductor die 106. Generally, the thicknessof the metallization layers may remain constant, or may increase towarda face 140A of the semiconductor die 106 and a face 140B of thesemiconductor die 104. As a specific example, the metallization region110 may include sixteen metallization layers. The bottom sixmetallization layers (e.g., including the metallization layer 130) mayhave the same thickness, followed by four metallization layers that are(as a non-limiting example) three to four times thicker than the bottommetallization layers, followed by two metallization layers (e.g., themetallization layers 132 and 134) that are (for example and withoutlimitation) ten times thicker than the bottom metallization layers.

In various examples, different metallization layers may be used fordifferent purposes, which may depend on the thickness of themetallization layers. The density of routing which may be implementedusing a metallization layer may decrease as the thickness of ametallization layer increases. However, the resistivity of ametallization layer may also decrease as the thickness of ametallization layer increases. Thus, in some examples, thickermetallization layers, such as the metallization layers 132 and 134 maybe configured for power distribution and/or global clock distribution.Thinner metallization layers, such as the metallization layer 130 may beconfigured for local signal routing, such as to connect localtransistors (e.g., to the transistor 126). Other metallization layers(e.g., with a thickness between the metallization layer 130 and themetallization layers 132 and 134) may be configured for bussing (e.g.,between an electronic circuit comprising the transistor 126 and anelectronic circuit comprising a transistor 142), lower level clockdistribution, and/or power routing.

Face-To-Face Dies with Enhanced Power Delivery Using TSVs

As described herein, one or more TSVs, such as the TSV 122 and/or theTSV 120 may extend from the semiconductor substrate 108 of thesemiconductor die 106 on an insulated path through at least onemetallization layer of the metallization region 110 to electrically andmechanically connect to a different metallization layer(s) of themetallization region 110 to supply power to the semiconductor die 104,to the different metallization layer(s), and to the components connectedto the different metallization layer(s). In the example shown, the TSV120 extends through the metallization layer 130 and each metallizationlayer below the metallization layer 132 in the metallization region 110to contact the metallization layer 132. However, in other examples a TSVmay extend through any number of metallization layers to contact anymetallization layer of the metallization region 110. For example, wherethe metallization region 110 includes two metallization layers, the TSVmay extend through the bottom metallization layer to contact the topmetallization layer. Also, in the example shown, rather than contactingthe metallization layer 132, the TSV may contact the metallization layer134 or any other metallization layer above the metallization layer 130.

By extending the TSV through at least one metallization layer of themetallization region 110, power distribution to the semiconductor die104 may be enhanced. For example, this may reduce the resistance of thepower supply path to the semiconductor die 104, as a TSV typically haslow resistance. The power supply path may run from the interface region114 of the semiconductor die 106 to the TSV 120, through themetallization layer 132 (e.g., a metallization segment 146), throughvias in the interlayer dielectric layer 136, through the metallizationlayer 134 (e.g., a metallization segment 148), and through the interfaceregion 112 to the interface region 124 of the semiconductor die 104.Resistance may further be reduced by allowing for the TSV to connect toa thicker metallization layer than would otherwise be possible. Forexample, the metallization layer 130 may be the thinnest and most highlyresistive of the metallization layers in the metallization region 110,and may be bypassed by extending the TSV 120 through the metallizationlayer 130.

The number of metallization layers in the metallization region 110 thata TSV is extended through and the thickness of the metallization layerthat the TSV contacts may vary depending on the design of theface-to-face arrangement 102 and the circuit components and electroniccircuits included in the face-to-face arrangement 102. For example,these factors may vary depending on the routing and layout requirementsof the face-to-face arrangement 102, as extending a TSV may introducerouting blockage in the metallization region 110. Also, these factorsmay vary depending on the power distribution requirements of theface-to-face arrangement 102. In the example shown, the TSV 120 isconfigured to supply power to circuit components in both thesemiconductor die 104 and the semiconductor die 106. For example, fromthe metallization layer 132, power may be distributed to circuitcomponents such as the transistor(s) 126 through a routing path 144 inthe metallization region 110 to reach the semiconductor substrate 108.The routing path 144 includes metallization arranged in a column, butthis arrangement may vary.

In the present example, the semiconductor die 104 and the semiconductordie 106 have substantially the same power distribution requirements. Forexample, the semiconductor die 104 and the semiconductor die 106 mayinclude the same electronic circuitry. Thus, the TSV 120 is configuredto deliver substantially the same power to the semiconductor die 104 andthe semiconductor die 106. However, the TSV 120 may in other examples beconfigured to deliver more power to the semiconductor die 104 than thesemiconductor die 106 or more power to semiconductor die 106 than thesemiconductor die 104. In some embodiments, the TSV 120 may beconfigured to deliver power to the semiconductor die 104, but not to thesemiconductor die 106 or not to a circuit component in the semiconductorsubstrate 108 of the semiconductor die 106. Also, while the TSV 120 andthe TSV 122 both contact the same metallization layer in the exampleshown, different TSVs within the semiconductor die 106 may extendthrough a different number of metallization layers to contact differentmetallization layers.

In various embodiments, the interface region 112 of the semiconductordie 106 may be formed on the metallization region 110 and mayelectrically and mechanically couple the semiconductor die 106 to thesemiconductor die 104. For example, the semiconductor die 104 may bemounted face-to-face with the semiconductor die 106 to form anelectrical and mechanical interface 150 at the interface region 112 ofthe semiconductor die 106 and the interface region 124 of thesemiconductor die 104.

Various techniques may be used to form the interface region 112 of thesemiconductor die 106 and the interface region 124 of the semiconductordie 104 so as to provide the electrical and mechanical interface 150.The interface region 112 and the interface region 114 may vary dependingon various factors, such as the desired characteristics for theelectrical and mechanical interface 150. As an example, the interfaceregion 112 and the interface region 114 may use a different techniqueand/or comprise different materials when only power is to be transferredacross the electrical and mechanical interface 150, as opposed to asignal(s) and power. FIG. 1B shows an example of the interface region112 and the interface region 114 along with an example of thesemiconductor die 104.

With reference to FIG. 1B, FIG. 1B is a diagram of an examplecross-section of a face-to-face arrangement 102 of semiconductor dies,in accordance with some embodiments of the present disclosure. In theexample of FIG. 1B, the interface region 112 and the interface region114 each include bonding dielectric (e.g., bonding oxide) and inter-dieinterface pads (e.g., formed from one or more bump pad layers and/orinter-die interface pad layers) that forms the electrical and mechanicalinterface 150. By way of example, the bonding dielectric may include abonding dielectric layer 152 (e.g., a bonding oxide layer). Also by wayof example, inter-die interface pads may include bump pads in thebonding dielectric layer 152, of which bump pads 154, 156, and 158 areindividually labeled. The bump pads 154 and 156 may be used to supplypower to the semiconductor die 104 and the interface region 112. Bumppad vias, such as a bump pad via 160, may be used to connect the bumppads 154 and 156 to the metallization layer 134. The bump pad 158 may,for example, be used to communicate a signal between the semiconductordie 104 and the semiconductor die 106. Any number of bump pads may beused to facilitate the exchange of power and/or signals between thesemiconductor die 104 and the semiconductor die 106.

The interface region 124 of the semiconductor die 104 may be similar tothe interface region 112 of the semiconductor die 106, with similarlydepicted elements representing corresponding features in the interfaceregion 112. However, in other examples, the interface region 124 mayinclude different elements than the interface region 112. As indicatedin FIG. 1B, the interface region 124 of the semiconductor die 104 mayreceive power from the TSV 120, which may be delivered to an electricalcircuit(s) comprising one or more circuit components, such as atransistor 162 formed at least partially in a semiconductor substrate164 of the semiconductor die 104 (e.g., using one more metallizationlayers in a metallization region 166).

The description of the semiconductor substrate 108 and the semiconductordie 106 may apply to the semiconductor substrate 164 and thesemiconductor die 104 and is therefore not repeated. However, theexamples may be mixed and matched such that the semiconductor substrate108 may comprise similar or different material than the semiconductorsubstrate 164. Similarly, the description of the metallization region110 and the semiconductor die 106 may apply to metallization region 166and the semiconductor die 104 and is therefore not repeated (e.g., thesame or a different number of layers may be included of similar ordifferent thicknesses). However, in some embodiments the semiconductordie 104 does not include the metallization layers 166 and/or may includea single metallization layer.

In the example of FIG. 1B, the semiconductor die 106 and thesemiconductor die 104 may be fabricated using the same mask set and thesame base wafer material. This allows for reduced cost by avoiding anadditional mask set. Further, device yields may be increased, forexample, as fabrication can be tailored to a single design.

As an example of fabricating the face-to-face arrangement 102, a wafercomprising the semiconductor substrate 108 may be processed to fabricatethe semiconductor die 106 comprising the metallization region 110. Theinterface region 112 may be formed on the metallization region 110 andthe wafer may be diced, or singulated, to form individual dies includingthe semiconductor die 106.

Also, a different wafer comprising the semiconductor substrate 164 maybe processed to fabricate the semiconductor die 104 comprising themetallization region 166. This processing may use the same mask set usedfor the semiconductor die 106 (or a different mask set in someembodiments). The interface region 124 may be formed on themetallization region 166. This processing may use the same mask set asused for the interface region 112 of the semiconductor die 106, or adifferent mask set. A pick and place machine may be used to mount thesingulated dies formed from the semiconductor substrate 108 with therespective unsingulated dies formed from the semiconductor substrate 164in face-to-face arrangements. This may form the face-to-face arrangement102. The singulated dies may then be thinned and the TSVs, such as theTSV 120 and the TSV 122 may be revealed. Subsequently, the interfaceregion 114 may be formed and the face-to-face arrangements may besingulated.

In some embodiments, the semiconductor die 104 is bilaterallysymmetrical to the semiconductor die 106 (and/or the mask set(s) used toform the semiconductor dies 104 and 106), as indicated by symmetry line170. When mounting the semiconductor die 106 and the semiconductor die106 in the face-to-face arrangement 102, the semiconductor die 106 maybe rotated and flipped around the symmetry line 170 (like book pages) toalign symmetrically-positioned contact points on the interface regions112 and 124. Other types of symmetry are covered by the disclosure, suchas quadrilateral symmetry and/or rotational symmetry. For example, thesemiconductor die 106 may be rotated 180 degrees and flipped around thesymmetry line 170 to align symmetrical contact points on the interfaceregions 112 and 124.

Where the semiconductor dies (and/or masks and/or surface contacts onthe face of the dies) are symmetrical, in some embodiments, one or morestructures in the semiconductor die 106 may have a correspondingstructure in the semiconductor die 104 that is configured for adifferent purpose or function than in the semiconductor die 106. Forexample, FIG. 1B shows a structure 176 (an electrically conductivestructure) of the semiconductor die 106 (including at least the TSVs 120and 122, connected metallization segments, such as the metallizationsegments 146 and 148, and connected microvias, such as those of therouting path 144), which may correspond to a structure 178 of thesemiconductor die 104. In the semiconductor die 106, the structure 176may be configured to supply power to the semiconductor die 104. In someembodiments, the structure 176 for purposes of this description does notrefer to connected components (e.g., the bump pad via 160 and the bumppads 154 and 156) in the interface region 112, while in others it may.For example, the interface region 124 and the interface region 112 maynot include analogous and/or duplicate structure. In the semiconductordie 104, the structure 178 may be configured to supply power to anelectronic circuit in the semiconductor substrate 164 (e.g., using bumppad vias in the interface region 112, such as the bump pad via 160 andbump pads, such as the bump pads 154 and 156), may remain unused orinactive (e.g., electrically inert) as a vestigial structure (e.g., notused to carry signals and/or power), or may be configured to perform adifferent function, such as to supply power to a semiconductor die(e.g., via one or more portions of the structure 178 that correspond tothe TSVs 120 and/or 122) and/or electrical component on thesemiconductor die 104 (e.g., via the interface region 124 which may beconfigured similar to or different than the interface region 112 withrespect to bump pad vias and bump pads) in embodiments that includethose additional elements.

FIG. 1B also shows a structure 182 (e.g. including connectedmetallization segments and microvias) of the semiconductor die 104,which may correspond to a structure 184 of the semiconductor die 106.Similar to the structures 176 and 178, the structures 182 and 184 may bean example of one or more corresponding structures that are configuredfor a different purpose or function for the semiconductor dies 104 and106. Also similar to the structures 176 and 178, in some embodiments,the structures 182 and 184 for purposes of this description do not referto connected components (e.g., bump pad vias and bump pads in theinterface regions 112 and 124, while in others they may. As indicated bythe region 172, the structures 178 and 182 may be configured to connectand/or align across the semiconductor dies 104 and 106. A similarconfiguration is shown for a region 174. In some embodiments, suchregions may be vestigial and may not be used for characterization of theface-to-face arrangement 102.

While the structure 176 and the structure 178 are substantially similarin FIG. 1B, the corresponding structures may be different from oneanother. For example, even where the same masks are used to form thestructures in the semiconductor dies 104 and 106, the correspondingstructures may be different. As an example, TSVs may not be formed inthe semiconductor die 104, the region 172, and/or the region 174.Referring now to FIG. 1C, FIG. 1C is a diagram of an examplecross-section of a face-to-face arrangement 102 of semiconductor dies,in accordance with some embodiments of the present disclosure. In thisexample, TSVs are not formed in the semiconductor die 104. Thus, thestructure 178 may not include TSVs that correspond to the TSVs 120 and122 of the structure 176, but may otherwise be similar. Additionally oralternatively, as described, portions of the structure 178 in theinterface region 124 may be different than portions of the structure 176in the interface region 112 (or no portion of the structure 178 may bein the interface region 124).

FIG. 1B also shows an example of the interface region 114 of thesemiconductor die 106. In the example of FIG. 1B, the interface region114 includes microbumps, such as a microbump 190A and a microbump 190B,which may serve as power and/or Input/Output (IO) terminals of theface-to-face arrangement 102. Thus, the interface region 114 maycomprise a communications and/or power interface to the face-to-facearrangement 102. For example, the microbump 190A and the microbump 190Bmay be configured as power supply terminals of the face-to-facearrangement 102. The interface region 114 may further include one ormore backside redistribution layers, such as a backside redistributionlayer 194. The interface region 114 may vary depending on such factorsas the packaging used to house the face-to-face arrangement 102,fabrication constraints or technologies, whether the semiconductor die104 or the semiconductor die 104 is the top die or the bottom die in theface-to-face arrangement 102, and/or whether there are additionalsemiconductor dies (e.g., in a face-to-face arrangement) and/orelectrical components stacked on the face-to-face arrangement 102, etc.

Now referring to FIG. 2, FIG. 2 is a diagram of an example cross-sectionof a semiconductor package 200 that includes a face-to-face arrangement102 of semiconductor dies, in accordance with some embodiments of thepresent disclosure. In the semiconductor package 200, the face-to-facearrangement 102 is electrically and mechanically coupled to aninterposer 202 by microbumps 290, which may include the microbumps 190Aand 190B of FIG. 1B. The interposer 202 may be electrically andmechanically coupled to a package substrate 204 by solder bumps 210,which may be C4 bumps. Also, the package substrate 204 includes solderballs 212, which may serve as terminals or pins of the semiconductorpackage 200. The semiconductor package 200 may include other elementsnot shown, such as encapsulant and additional dies and/or electricalcomponents. One or more of the solder balls 212 may be a package powersupply terminal of the semiconductor package 200, and may beelectrically connected to the interface region 114 of the semiconductordie 106, such as by the microbump 190A and the microbump 190B. One ormore of the solder balls 212 may also be a package signal, or IOterminal of the semiconductor package 200, and may be electricallyconnected to the interface region 114 of the semiconductor die 106, suchas by one or more of the microbumps 290. The semiconductor package 200is provided as one suitable example of a semiconductor package, butother packaging types and technologies may be used in disclosedembodiments.

Face-To-Face Dies with a Void for Enhanced Inductor Performance

Aspects of the disclosed approaches provide for forming an inductor overa semiconductor substrate of one or both dies in a face-to-face diearrangement while reducing the parasitic capacitance between theinductor and the adjacent die. In disclosed embodiments, thesemiconductor device may include a void (e.g., an air gap) between theinductor and the adjacent die to reduce the parasitic capacitancebetween the inductor and the adjacent die. The void may be etched ininterface layers (e.g., comprising inter-die interface pads anddielectric material) between the semiconductor dies, and may extendalong the length of the inductor. FIG. 3A shows one such example of asuitable face-to-face arrangement of semiconductor dies, but manydifferent variations are within the score of the present disclosure.

Now referring to FIG. 3A, FIG. 3A is a diagram of an examplecross-section of a face-to-face arrangement 302 of semiconductor diesthat includes a void for an inductor, in accordance with someembodiments of the present disclosure.

The face-to-face arrangement 302 may be the same as or different thanthe face-to-face arrangement 102 of FIGS. 1A and/or 1B. In theface-to-face arrangement 302, one or more inductors may be formed overthe semiconductor substrate 108 of the semiconductor die 106.

Examples in FIG. 3A include an inductor 304 and an inductor 306. Theinductors 304 and 306 may be included in the face-to-face arrangement302 for, as examples, high speed clock operation and/or power filtering(e.g., of power received from a power supply terminal of theface-to-face arrangement 302). In embodiments where the inductor 304and/or the inductor 306 are used for clocking, the inductor may connectto phase-locked loop (PLL) circuitry (to generate a clock signal) andmay not include a connection to a TSV (or a power supply path) and/or tooutside of the semiconductor package 200.

In the example shown, the inductors 304 and 306 are formed in theinterface region 112. In other examples, one or more inductors may inaddition or instead be formed in a different region, such as themetallization region 110. As shown, the face-to-face arrangement 302includes a void 308 between the inductor 304 and the semiconductor die104 and a void 310 between the inductor 306 and the semiconductor die104. The voids 308 and 310 may be an air gap configured to reduce theparasitic capacitance between the inductors 304 and 306 and thesemiconductor die 104. The voids 308 and 310 may extend along the lengthof the inductors 304 and 306 respectively along a direction parallel tothe face 140A of the semiconductor die 106. The voids 308 and 310 mayalso extend from a distal plane on the face 140A of the semiconductordie 106 to the inductors 304 and 306 respectively. For example, thevoids 308 and 310 may be formed in the surface of the interface region112 by etching the voids 308 and 310 in the bonding dielectric layer152. In other examples, the voids may be etched in additional ordifferent portions of the interface region 112. Also in someembodiments, the voids 308 and 310 may be formed at least partially onthe semiconductor die 104. In some examples, the inductor 304 or 306 isat least partially on a distal plane on the face 140A of thesemiconductor die 106, and the void 308 or 310 is formed on a distalplane on the face 140B of the semiconductor die 104 rather than on thesemiconductor die 106 (e.g., by etching the void(s) in the interfaceregion 124).

The semiconductor die 106 may also include a voided region between theinductor and the backside of the semiconductor die 106 to avoidparasitic capacitance between the inductor and elements of thesemiconductor die 106. For example, a voided region 312 is shown, whichmay extend to the backside of the semiconductor die 106. The voidedregion 312 may also extend along the length of the inductor 304, similarto the void 308. The voided region 312 is configured to be floating.Thus, while conductive material, such as metallization may be in thevoided region 312 (e.g., as fill material to satisfy design rules), theconductive material is floating (e.g., comprising non-signal carryinglayers) so as to avoid parasitic capacitance with the inductor 304. FIG.3B is used to describe additional examples of the face-to-facearrangement 302.

FIG. 3B is a diagram of an example cross-section of the face-to-facearrangement 302 of semiconductor dies that includes a void for aninductor, in accordance with some embodiments of the present disclosure.As shown in FIG. 3B, the semiconductor die 104 may also include a voidedregion 314 for the inductor 304, which may be similar to the voidedregion 312. FIG. 3B also shows an example where the semiconductor die104 includes an inductor 316, a void 318, and a voided region 320, whichmay be similar to or different than the inductor 304, the void 308, andthe voided region 312, respectively. Further, the semiconductor die 106includes a voided region 322, which may be similar to the voided region314. Thus, one or both of the semiconductor dies 104 or 106 may includean inductor and corresponding void. Further, the inductor and void maybe formed in different layers in each semiconductor die. Also, invarious embodiments, an inductor (e.g., the inductor 304, 306, and/or316) may optionally be formed in one semiconductor die and connected toelectronic circuity (e.g., to provide a clock, etc.) in the other die inaddition to or instead of the semiconductor die. While like FIG. 3B,FIG. 1B shows the inductors and voids, the face-to-face arrangement 102may be provided without one or more of those elements. Also, while likeFIG. 1B, FIG. 3B shows TSVs that extend through at least onemetallization layer, the face-to-face arrangement 302 may be providedwithout one or more of those elements.

Face-To-Face Dies with Probe Pads for Pre-Assembly Testing

Aspects of the disclosed approaches provide for one or bothsemiconductor dies in a face-to-face arrangement including at least oneprobe pad layer formed on a face of the die to allow the die to beindividually tested prior to assembly of the dies. Thus, faulty dies maybe discarded individually so they are not included in a compositesemiconductor device, or dies may be better matched, thereby increasingdevice yields. In some embodiments, a semiconductor die may be tested(e.g., at a fabrication facility pre-dicing), then additional interfacelayers (e.g., comprising inter-die interface pads and dielectricmaterial) may be formed over the probe pad layer and used to bond thesemiconductor dies in a face-to-face arrangement to form a compositesemiconductor device. FIGS. 4A and 4B show one such example used todescribe testing, then forming additional interface layers over asemiconductor die prior to including the semiconductor die aface-to-face arrangement of semiconductor dies, but many differentvariations are within the score of the present disclosure.

FIG. 4A is a diagram of an example cross-section of the semiconductordie 106 including probe pads for testing prior to including thesemiconductor die 106 in the face-to-face arrangement 102 ofsemiconductor dies, in accordance with some embodiments of the presentdisclosure. The semiconductor die 106 of FIGS. 4A and 4B may correspondto the semiconductor die 106 during fabrication and pre-assembly intothe face-to-face arrangement 102.

The interface region 112 of FIG. 4A is formed on a die region 410 on theface 140B of the semiconductor die 106. The die region 410 is showngenerically to indicate the broad applicability of the approachesdescribed with respect to FIGS. 4A and 4B, but may in some embodimentsinclude the metallization region 110 and the semiconductor substrate108. In some embodiments, the interface region 114 is not yet formed onthe semiconductor die 106.

The interface region 112 of FIG. 4A includes a plurality of probe pads,of which probe pads 406 and 408 are shown. The probe pads may comprise,for example, aluminum probe pads formed from a probe pad layer(s). Inembodiments where the interface region 112 includes at least oneinductor, such as the inductor 304 or the inductor 306, one or more ofthe inductors may also be formed from the probe pad layer(s), as shown,and/or from a different layer(s). The probe pads may be configured totest one or more electronic circuits in the semiconductor die 106, suchas an electronic circuit comprising the transistor 126 and/or 142. Forexample, the probe pads may be electrically connected to the electroniccircuit(s) by the metallization region 110 for testing. As an example,the semiconductor die 106 may be tested prior to dicing, along withother similar semiconductor dies on the wafer. Further, this testing mayoccur at the fabrication facility used to fabricate the wafer.

Subsequent to testing the wafer comprising the semiconductor die 106,the wafer may undergo further processing (e.g., at the fabricationfacility) to produce the semiconductor die 106 of FIG. 4B. FIG. 4B is adiagram of an example cross-section of the semiconductor die 106including additional interface layers formed over the probe pads of FIG.4A, in accordance with some embodiments of the present disclosure. Theadditional processing may include forming one or more bonding dielectriclayers, such as the bonding dielectric layer 152 over the probe padlayer and/or probe pads. Additionally, any number of inter-die interfacepads, such as the bump pads 154, 156, or 158 may be formed in thebonding dielectric layer 152. Further, in embodiments that include oneor more inductors, voids—such as the voids 308 or 310—may be formed inthe bonding dielectric layer 152. The semiconductor die 106 may then bemounted to the semiconductor die 104 in the face-to-face arrangement 102using the bonding dielectric layer 152.

In the face-to-face arrangement 102, the probe pads of the probe padlayer may be insulated from the semiconductor die 104 and may remaininactive during operation of the semiconductor die 106. Thus, the probepads may only be operated for testing of the semiconductor die 106pre-assembly, but may remain as vestiges and electrically inert in theface-to-face arrangement 102. In other examples, the probe pads may beconfigured or reconfigured for operation of the semiconductor die 106and/or the semiconductor die 104 in the face-to-face arrangement 102.

While FIGS. 4A and 4B are described with respect to the semiconductordie 106, FIGS. 4A and 4B may also apply to the semiconductor die 104.For example, the interface region 124 of the semiconductor die 104 maybe formed similar to the interface region 112, including testing thesemiconductor die 104 at the fabrication facility, then performingadditional processing to arrive at the configuration of FIG. 4B.However, in some embodiments the semiconductor die 104 may include probepads in the interface region 124 while the semiconductor die 106 doesnot include probe pads in the interface region 112, or the semiconductordie 106 may include probe pads in the interface region 112 while thesemiconductor die 104 does not include probe pads in the interfaceregion 124.

To form the face-to-face arrangement 102, the wafer comprising thesemiconductor die 106 may be singulated and a pick and place machine maybe used to mount the singulated dies formed from the semiconductorsubstrate 108 with the respective unsingulated dies formed from thesemiconductor substrate 164 in face-to-face arrangements including theface-to-face arrangement 102. In embodiments where the semiconductorsubstrate includes TSVs, the singulated dies may then be thinned and theTSVs, such as the TSV 120 and the TSV 122 may be revealed. Subsequently,the interface region 114 may be formed and the face-to-face arrangementsmay be singulated. The interface region 114 may be used to test thesemiconductor die 104 and/or the semiconductor die 106, such as bytesting a composite semiconductor device (e.g., a composite logiccircuit) formed from the semiconductor die 104 and the semiconductor die106 (e.g., in the semiconductor package 200 and/or prior to inclusion ina semiconductor package). This testing may occur at a testing facilityseparate from the fabrication facility and may use microbumps in theinterface region 114, such as the microbump 190A and/or the microbump190B (e.g. power and signal terminals used during regular operation)and/or may use backside probe pads in the interface region 114, such asa probe pad 192A and/or a probe pad 192B formed in a backside probe padlayer (e.g. prior to formation of the microbumps). As the semiconductordies may be tested pre-assembly, faulty dies may be discarded so theyare not included in a face-to-face arrangement and/or dies may bematched, thereby increasing device yields.

Referring now to FIG. 4C, FIG. 4C is a diagram of an example top view ofa testing tile structure 416 which may be included in semiconductor die106, in accordance with some embodiments of the present disclosure. Thesemiconductor die 106 may include any number of testing tile structures,which may appear similar to the testing tile structure 416 and may bearranged in a grid-like arrangement. The testing tile structure 416includes the probe pads 406 and 408, as well as a probe pad 418 and aprobe pad 420. In other embodiments the testing tile structure 416 mayinclude a different number of probe pads. During testing, pins oftesting hardware may electrically and mechanically interface with thetesting tile structure 416 at the probe pads. As an example, the probepads may each be approximately 50×50 microns, and larger than theinter-die interface pads (e.g., the bump pads 154, 156, and 158).

The probe pad 406 may be configured as a power supply terminal of thetesting tile structure 416 and the probe pad 408 may be configured as aground pad of the testing tile structure 416 during the testing.Further, the probe pads 418 and 420 may be configured as respectivesignal terminals of the testing tile structure 416 during the testing.While the testing tile structure 416 includes two signal terminals inthe example shown, the testing tile structure 416 may be used to testmore than two signals in the semiconductor die 106 by serializing thesignals. Each probe pad may be electrically connected to a respectiveportion of a redistribution layer, as shown in FIG. 4C. In the exampleshown, the portions of the redistribution layer include interdigitatedfingers, or rows. Each node on a finger may be coupled to an underlyingvia and routed to a corresponding circuit element(s) in thesemiconductor substrate 108 (e.g., the transistor 126). While thetesting tile structure 416 is shown, embodiments of the presentdisclosure may not use a testing tile structure for testing. Also, thesemiconductor die 104 may include a similar or different testingstructure.

Referring now to FIG. 4D, FIG. 4D is a diagram of an example top view ofan arrangement 430 of testing tile structures 416 which may be includedin the semiconductor die 106, in accordance with some embodiments of thepresent disclosure. While only eight testing tile structures 416 areshown in FIG. 4D, the semiconductor die 106 may include, as an example,thousands of testing tile structures 416. In a specific and non-limitingexample, the semiconductor die 106 may by approximately 20 millimetersby 20 millimeters and a testing tile structure 416 may be approximately200 micrometers by 200 micrometers. Thus, as many as 10,000 testing tilestructures 416 may fit in the arrangement 430. However, in the presentexample, the region 432 does not include a testing tile structure 416.Instead, the region 432 may include one or more other testing tilestructures and/or testing structures, or may not include any probe padsor testing structures. In some examples, the region 432 corresponds to acrossbar configured for inter-die communication of signals between thesemiconductor die 104 and the semiconductor die 106 in the face-to-facearrangement 102. The crossbar may be used to communicatively couple aprocessing unit in the semiconductor die 104 with a processing unit inthe semiconductor die 106.

Although FIGS. 4C and 4D are described with respect to the semiconductordie 106, FIGS. 4C and 4D may also apply to the semiconductor die 104.For example, the semiconductor die 104 may include similar or differenttesting structures (e.g., tiles) as the semiconductor die 104 in asimilar or different arrangement.

In embodiments where the semiconductor die 106 comprises a processingunit, the testing tile structures 416 may each correspond to one or morerespective processing cores of the processing unit (e.g., thatunderlines the testing tile structure 416). Using the testing tilestructures 416, each processing core(s) may be individually tested. Forexample, where the semiconductor die 106 comprises a GPU, each testingtile structure 416 may correspond to a respective SM and may be used totest the SM. The semiconductor die 106 may be configured (e.g., by thetesting hardware) to bypass faulty cores and/or SMs based on the testingthe semiconductor die 106. Further, the semiconductor die 106 may bematched to another component for inclusion in a face-to-face arrangementbased on the testing of the semiconductor die 106. For example, thesemiconductor die 106 and the semiconductor die 104 may each be testedand selected for inclusion in the face-to-face arrangement 102 based onthe number of cores and/or SMs that pass the testing (and/or otherperformance characteristics identified by the testing). This may be doneso that the composite semiconductor device collectively includes athreshold number of active cores or otherwise satisfies predeterminedperformance criteria.

Now referring to FIG. 5, FIG. 5 is a flow diagram showing a method 500for testing at least one semiconductor die prior to assembly in aface-to-face arrangement with another semiconductor die, in accordancewith some embodiments of the present disclosure. The method 500 isdescribed using the semiconductor die 104 and the semiconductor die 106,by way of example only. Further, while the method 500 is described withthe semiconductor die 106 being tested, an instance of the method 500may additionally or alternatively be used with the semiconductor die 104being tested in place of the semiconductor die 106.

The method 500, at block B502, includes testing a first semiconductordie using probe pads formed on a face of the first semiconductor die.For example, testing equipment may test the semiconductor die 106 byprobing the probe pads 406 and 408 of FIG. 4A. In embodiments where thesemiconductor die 106 includes the testing tile structure 416 of FIG.4C, the probe pads 418 and 420 may also be probed to test thesemiconductor die 106.

The method 500, at block B504, includes forming at least an interfacelayer of the first semiconductor die over the probe pads. For example,after testing the semiconductor die 106, additional interface layers ofthe interface region 112 may be formed over the probe pads 406 and 408to result in FIG. 4B. As shown, the interface layers may include thebonding dielectric layer 152 and an inter-die interface pad layer(s)used to form inter-die interface pads such as the bump pads 154, 156,and 158.

The method 500, at block B506, includes mounting the first semiconductordie face-to-face with a second semiconductor die using the interfacelayer to couple at least one inter-die interface pad of the firstsemiconductor die to at least one inter-die interface pad of a secondsemiconductor die. For example, a pick and place machine may be used tomount the semiconductor die 106 to the semiconductor die 106 using thebonding dielectric layer 152 to couple the bump pads 154, 156, and 158to corresponding bump pads of the semiconductor die 104, as in FIGS. 1Band 3B. In other examples, the bonding dielectric layer 152 may not beused, such as where the inter-die interface pad layer is sufficient(e.g., the top surface of the semiconductor die 106 may be a singleinter-die interface pad). As described herein, the semiconductor die 106and the semiconductor die 104 may form at least part of a compositesemiconductor device, which may be tested through the backside of thesemiconductor die 106, the semiconductor die 104 (in embodiments whereprobe pads are included on the backside of the semiconductor die 104),and/or other semiconductor dies which may be in a stack with thosesemiconductor dies.

Thus, various approaches for enhancing semiconductor arrangements thatinclude face-to-face semiconductor dies have been provided herein. Theseapproaches may be mixed and matched in any suitable combination in orderto achieve semiconductor devices with desired characteristics.

As used herein, a recitation of “and/or” with respect to two or moreelements should be interpreted to mean only one element, or acombination of elements. For example, “element A, element B, and/orelement C” may include only element A, only element B, only element C,element A and element B, element A and element C, element B and elementC, or elements A, B, and C. In addition, “at least one of element A orelement B” may include at least one of element A, at least one ofelement B, or at least one of element A and at least one of element B.

The subject matter of the present disclosure is described withspecificity herein to meet statutory requirements. However, thedescription itself is not intended to limit the scope of thisdisclosure. Rather, the inventors have contemplated that the claimedsubject matter might also be embodied in other ways, to includedifferent steps or combinations of steps similar to the ones describedin this document, in conjunction with other present or futuretechnologies. Moreover, although the terms “step” and/or “block” may beused herein to connote different elements of methods employed, the termsshould not be interpreted as implying any particular order among orbetween various steps herein disclosed unless and except when the orderof individual steps is explicitly described.

1. A semiconductor device comprising: a first semiconductor die having,a semiconductor substrate, an inductor, and a void; and a secondsemiconductor die having a semiconductor substrate; wherein the firstsemiconductor die is mounted face-to-face with the second semiconductordie; wherein the inductor of the first semiconductor die is between thesemiconductor substrate of the first semiconductor die and thesemiconductor substrate of the second semiconductor die; and wherein thevoid is formed in the first semiconductor die and is between theinductor of the first semiconductor die and the second semiconductordie.
 2. The semiconductor device of claim 1, wherein the void extendsfrom the inductor of the first semiconductor die to a face of the secondsemiconductor die.
 3. The semiconductor device of claim 1, wherein aportion of the void is further formed in a portion of the secondsemiconductor die.
 4. (canceled)
 5. The semiconductor device of claim 1,wherein the void is etched in a bonding dielectric material of the firstsemiconductor die and the bonding dielectric material mechanicallycouples the first semiconductor die to the second semiconductor die. 6.The semiconductor device of claim 1, wherein the void extends through aninter-die interface pad layer of the first semiconductor die to reachthe inductor in the first semiconductor die.
 7. The semiconductor deviceof claim 1, wherein the first semiconductor die further includesbackside interface layers to communicate with the first semiconductordie.
 8. The semiconductor device of claim 1, wherein the secondsemiconductor die further includes backside interface layers tocommunicate with the second semiconductor die.
 9. The semiconductordevice of claim 1, wherein the void reduces parasitic capacitancebetween the inductor and the second semiconductor die.
 10. Asemiconductor device comprising: a first semiconductor die having, asemiconductor substrate, and an inductor; a second semiconductor diehaving a semiconductor substrate; an inter-die interface pad layercommunicatively coupling the first semiconductor die and the secondsemiconductor die; and a void formed in the inter-die interface padlayer; wherein the first semiconductor die is mounted face-to-face withthe second semiconductor die; wherein the inductor of the firstsemiconductor die is between the semiconductor substrate of the firstsemiconductor die and the semiconductor substrate of the secondsemiconductor die.
 11. The semiconductor device of claim 10, wherein theinter-die interface pad layer and the void are formed in the firstsemiconductor die.
 12. The semiconductor device of claim 10, wherein theinter-die interface pad layer and the void are formed in the secondsemiconductor die.
 13. The semiconductor device of claim 10, wherein thevoid is formed in a portion of the first semiconductor die and a portionof the second semiconductor die.
 14. The semiconductor device of claim10, wherein the inter-die interface pad layer is a bump pad layercomprising a plurality of bump pads.
 15. The semiconductor device ofclaim 10, wherein the inter-die interface pad layer communicativelycouples a processing unit in the first semiconductor die and aprocessing unit in second semiconductor die.
 16. A semiconductor devicecomprising: a first semiconductor die having, a semiconductor substrate,and an inductor; a second semiconductor die having a semiconductorsubstrate; a bonding dielectric layer mechanically coupling the firstsemiconductor die to the second semiconductor die in a face-to-facearrangement; wherein the inductor of the first semiconductor die isbetween the semiconductor substrate of the first semiconductor die andthe semiconductor substrate of the second semiconductor die; and whereinthe void is etched in the bonding dielectric layer and is exposing theinductor.
 17. The semiconductor device of claim 16, further comprisinginter-die interface pads formed in the bonding dielectric layer andcommunicatively coupling the first semiconductor die and the secondsemiconductor die.
 18. The semiconductor device of claim 16, wherein thebonding dielectric layer is formed on the first semiconductor die. 19.The semiconductor device of claim 16, wherein the bonding dielectriclayer is formed on the second semiconductor die.
 20. The semiconductordevice of claim 16, wherein the inductor is connected to phase-lockedloop circuitry to generate a clock signal.
 21. The semiconductor deviceof claim 16, wherein the inductor is electrically connected to a powersupply terminal of the face-to-face arrangement to filter power receivedfrom the power supply terminal.